The present invention relates to a sealing apparatus, and particularly to an electron gun sealing apparatus for fixedly securing an electron gun to the neck of a bulb for a cathode ray tube.
Generally, an electron gun sealing apparatus serves to form a vacuum envelope, in the following manner: first, an electron gun is inserted into the neck of an unsealed bulb for a cathode ray tube then, the stem of the electron gun is welded to the neck of the bulb by heating the outer surface of the neck with a burner. The construction of such a sealing apparatus for welding the electron gun's stem and the bulb's neck is illustrated in FIG. 1 and will be described below.
A plurality of supporting frames 3 mounting bulbs 100 for cathode ray tubes are rotatably installed around the edge of a turntable 2. An electron gun support rod 4 is provided for inserting an electron gun 110 into a neck 101 of a bulb 100 mounted on each supporting frame 3. A pair of burners 5 supported by supporters 5a are installed around the turntable 2, and are spaced apart from each other. The supporting frame 3 and the electron gun support rod 4 are installed to be rotated at a predetermined revolution on the turntable 2. The electron gun support rod 4 is elevated and retracted by a raising and lowering means (not shown).
In order to seal the electron gun 110 in the neck 101 of the cathode ray tube using the conventional electron gun sealing apparatus constructed as above, first, the bulb 100 for the cathode ray tube is mounted to the supporting frame 3 which is installed on turntable 2. At the same time, the electron gun 110 is held by the support rod 4. Under these circumstances, the electron gun support rod 4 is elevated by the unseen raising and lowering means, thereby inserting the electron gun 110 into the neck 101 of bulb 100. While the supporting frame 3 and the electron gun support rod 4 are both rotated, the burners 5 installed around turntable 2 rotate through a predetermined angle and heat the neck 101 by applying a pilot flame and a main flame in a regular sequence. Therefore, the stem of the electron gun 110 and the neck 101 of the bulb 100 are fixedly welded to each other, completing the sealing process.
However, the above-described conventional electron gun sealing apparatus requires a sizable facility for the overall installation, resulting not only in occupying a large area, but also incurring high maintenance expenses. A particular disadvantage of the above sealing operation is that, since the turntable 2 is turned by predetermined angles along with rotating the bulb 100 and the electron gun support rod 4, the rotation of the turntable 2 forces the bulb mounted to the supporting frame to be under the influence of centrifugal force, repeatedly displacing the bulb, which in turn widens the range of sealing errors. Moreover, these conditions lead to variations in the seal and therefore inconsistent quality, thereby increasing the quantity of inferior products.